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diff --git a/src/util/util.c b/src/util/util.c
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+/*
+ This file is part of TALER
+ (C) 2014 Christian Grothoff (and other contributing authors)
+
+ TALER is free software; you can redistribute it and/or modify it under the
+ terms of the GNU General Public License as published by the Free Software
+ Foundation; either version 3, or (at your option) any later version.
+
+ TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along with
+ TALER; see the file COPYING. If not, If not, see <http://www.gnu.org/licenses/>
+*/
+
+/**
+ * @file util.c
+ * @brief Common utility functions
+ * @author Sree Harsha Totakura <sreeharsha@totakura.in>
+ * @author Florian Dold
+ * @author Benedikt Mueller
+ */
+
+#include "platform.h"
+#include "taler_util.h"
+#include <gnunet/gnunet_common.h>
+#include <gnunet/gnunet_util_lib.h>
+#include <gcrypt.h>
+
+#define CURVE "Ed25519"
+
+#define AMOUNT_FRAC_BASE 1000000
+#define AMOUNT_FRAC_LEN 6
+
+
+
+static void
+fatal_error_handler (void *cls, int wtf, const char *msg)
+{
+ LOG_ERROR("Fatal error in Gcrypt: %s\n", msg);
+ abort();
+}
+
+
+/**
+ * Initialize Gcrypt library.
+ */
+void
+TALER_gcrypt_init()
+{
+ gcry_set_fatalerror_handler (&fatal_error_handler, NULL);
+ TALER_assert_as(gcry_check_version(NEED_LIBGCRYPT_VERSION),
+ "libgcrypt version mismatch");
+ /* Disable secure memory. */
+ gcry_control (GCRYCTL_DISABLE_SECMEM, 0);
+ gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0);
+}
+
+
+/**
+ * Generate a ECC private key.
+ *
+ * @return the s-expression representing the generated ECC private key; NULL
+ * upon error
+ */
+gcry_sexp_t
+TALER_genkey ()
+{
+ gcry_sexp_t priv_sexp;
+ gcry_sexp_t s_keyparam;
+ int rc;
+
+ if (0 != (rc = gcry_sexp_build (&s_keyparam, NULL,
+ "(genkey(ecc(curve \"" CURVE "\")"
+ "(flags eddsa)))")))
+ {
+ LOG_GCRY_ERROR ("gcry_sexp_build", rc);
+ return NULL;
+ }
+ if (0 != (rc = gcry_pk_genkey (&priv_sexp, s_keyparam)))
+ {
+ LOG_GCRY_ERROR ("gcry_pk_genkey", rc);
+ gcry_sexp_release (s_keyparam);
+ return NULL;
+ }
+ gcry_sexp_release (s_keyparam);
+ if (0 != (rc = gcry_pk_testkey (priv_sexp)))
+ {
+ LOG_GCRY_ERROR("gcry_pk_testkey", rc);
+ gcry_sexp_release (priv_sexp);
+ return NULL;
+ }
+ return priv_sexp;
+}
+
+
+/**
+ * Parse money amount description, in the format "A:B.C".
+ *
+ * @param str amount description
+ * @param denom amount to write the result to
+ * @return GNUNET_OK if the string is a valid amount specification,
+ * GNUNET_SYSERR if it is invalid.
+ */
+int
+TALER_string_to_amount (const char *str, struct TALER_Amount *denom)
+{
+ unsigned int i; // pos in str
+ int n; // number tmp
+ unsigned int c; // currency pos
+ uint32_t b; // base for suffix
+
+ memset (denom, 0, sizeof (struct TALER_Amount));
+
+ i = n = c = 0;
+
+ while (isspace(str[i]))
+ i++;
+
+ if (0 == str[i])
+ {
+ printf("null before currency\n");
+ return GNUNET_SYSERR;
+ }
+
+ while (str[i] != ':')
+ {
+ if (0 == str[i])
+ {
+ printf("null before colon");
+ return GNUNET_SYSERR;
+ }
+ if (c > 3)
+ {
+ printf("currency too long\n");
+ return GNUNET_SYSERR;
+ }
+ denom->currency[c] = str[i];
+ c++;
+ i++;
+ }
+
+ // skip colon
+ i++;
+
+ if (0 == str[i])
+ {
+ printf("null before value\n");
+ return GNUNET_SYSERR;
+ }
+
+ while (str[i] != '.')
+ {
+ if (0 == str[i])
+ {
+ return GNUNET_OK;
+ }
+ n = str[i] - '0';
+ if (n < 0 || n > 9)
+ {
+ printf("invalid character '%c' before comma at %u\n", (char) n, i);
+ return GNUNET_SYSERR;
+ }
+ denom->value = (denom->value * 10) + n;
+ i++;
+ }
+
+ // skip the dot
+ i++;
+
+ if (0 == str[i])
+ {
+ printf("null after dot");
+ return GNUNET_SYSERR;
+ }
+
+ b = 100000;
+
+ while (0 != str[i])
+ {
+ n = str[i] - '0';
+ if (b == 0 || n < 0 || n > 9)
+ {
+ printf("error after comma");
+ return GNUNET_SYSERR;
+ }
+ denom->fraction += n * b;
+ b /= 10;
+ i++;
+ }
+
+ return GNUNET_OK;
+}
+
+
+/**
+ * FIXME
+ */
+struct TALER_AmountNBO
+TALER_amount_hton (struct TALER_Amount d)
+{
+ struct TALER_AmountNBO dn;
+ dn.value = htonl (d.value);
+ dn.fraction = htonl (d.fraction);
+ memcpy (dn.currency, d.currency, TALER_CURRENCY_LEN);
+
+ return dn;
+}
+
+
+/**
+ * FIXME
+ */
+struct TALER_Amount
+TALER_amount_ntoh (struct TALER_AmountNBO dn)
+{
+ struct TALER_Amount d;
+ d.value = ntohl (dn.value);
+ d.fraction = ntohl (dn.fraction);
+ memcpy (d.currency, dn.currency, sizeof(dn.currency));
+
+ return d;
+}
+
+
+/**
+ * Compare the value/fraction of two amounts. Does not compare the currency,
+ * i.e. comparing amounts with the same value and fraction but different
+ * currency would return 0.
+ *
+ * @param a1 first amount
+ * @param a2 second amount
+ * @return result of the comparison
+ */
+int
+TALER_amount_cmp (struct TALER_Amount a1, struct TALER_Amount a2)
+{
+ a1 = TALER_amount_normalize (a1);
+ a2 = TALER_amount_normalize (a2);
+ if (a1.value == a2.value)
+ {
+ if (a1.fraction < a2.fraction)
+ return -1;
+ if (a1.fraction > a2.fraction)
+ return 1;
+ return 0;
+ }
+ if (a1.value < a2.value)
+ return -1;
+ return 1;
+}
+
+
+/**
+ * Perform saturating subtraction of amounts.
+ *
+ * @param a1 amount to subtract from
+ * @param a2 amount to subtract
+ * @return (a1-a2) or 0 if a2>=a1
+ */
+struct TALER_Amount
+TALER_amount_subtract (struct TALER_Amount a1, struct TALER_Amount a2)
+{
+ a1 = TALER_amount_normalize (a1);
+ a2 = TALER_amount_normalize (a2);
+
+ if (a1.value < a2.value)
+ {
+ a1.value = 0;
+ a1.fraction = 0;
+ return a1;
+ }
+
+ if (a1.fraction < a2.fraction)
+ {
+ if (0 == a1.value)
+ {
+ a1.fraction = 0;
+ return a1;
+ }
+ a1.fraction += AMOUNT_FRAC_BASE;
+ a1.value -= 1;
+ }
+
+ a1.fraction -= a2.fraction;
+ a1.value -= a2.value;
+
+ return a1;
+}
+
+
+/**
+ * Perform saturating addition of amounts.
+ *
+ * @param a1 first amount to add
+ * @param a2 second amount to add
+ * @return sum of a1 and a2
+ */
+struct TALER_Amount
+TALER_amount_add (struct TALER_Amount a1, struct TALER_Amount a2)
+{
+ a1 = TALER_amount_normalize (a1);
+ a2 = TALER_amount_normalize (a2);
+
+ a1.value += a2.value;
+ a1.fraction += a2.fraction;
+
+ if (0 == a1.currency[0])
+ {
+ memcpy (a2.currency, a1.currency, TALER_CURRENCY_LEN);
+ }
+
+ if (0 == a2.currency[0])
+ {
+ memcpy (a1.currency, a2.currency, TALER_CURRENCY_LEN);
+ }
+
+ if (0 != a1.currency[0] && 0 != memcmp (a1.currency, a2.currency, TALER_CURRENCY_LEN))
+ {
+ GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "adding mismatching currencies\n");
+ }
+
+ if (a1.value < a2.value)
+ {
+ a1.value = UINT32_MAX;
+ a2.value = UINT32_MAX;
+ return a1;
+ }
+
+ return TALER_amount_normalize (a1);
+}
+
+
+/**
+ * Normalize the given amount.
+ *
+ * @param amout amount to normalize
+ * @return normalized amount
+ */
+struct TALER_Amount
+TALER_amount_normalize (struct TALER_Amount amount)
+{
+ while (amount.value != UINT32_MAX && amount.fraction >= AMOUNT_FRAC_BASE)
+ {
+ amount.fraction -= AMOUNT_FRAC_BASE;
+ amount.value += 1;
+ }
+ return amount;
+}
+
+
+/**
+ * Convert amount to string.
+ *
+ * @param amount amount to convert to string
+ * @return freshly allocated string representation
+ */
+char *
+TALER_amount_to_string (struct TALER_Amount amount)
+{
+ char tail[AMOUNT_FRAC_LEN + 1] = { 0 };
+ char curr[TALER_CURRENCY_LEN + 1] = { 0 };
+ char *result = NULL;
+ int len;
+
+ memcpy (curr, amount.currency, TALER_CURRENCY_LEN);
+
+ amount = TALER_amount_normalize (amount);
+ if (0 != amount.fraction)
+ {
+ unsigned int i;
+ uint32_t n = amount.fraction;
+ for (i = 0; (i < AMOUNT_FRAC_LEN) && (n != 0); i++)
+ {
+ tail[i] = '0' + (n / (AMOUNT_FRAC_BASE / 10));
+ n = (n * 10) % (AMOUNT_FRAC_BASE);
+ }
+ tail[i] = 0;
+ len = GNUNET_asprintf (&result, "%s:%lu.%s", curr, (unsigned long) amount.value, tail);
+ }
+ else
+ {
+ len = GNUNET_asprintf (&result, "%s:%lu", curr, (unsigned long) amount.value);
+ }
+ GNUNET_assert (len > 0);
+ return result;
+}
+
+
+
+/**
+ * Return the base32crockford encoding of the given buffer.
+ *
+ * The returned string will be freshly allocated, and must be free'd
+ * with GNUNET_free.
+ *
+ * @param buffer with data
+ * @param size size of the buffer
+ * @return freshly allocated, null-terminated string
+ */
+char *
+TALER_data_to_string_alloc (const void *buf, size_t size)
+{
+ char *str_buf;
+ size_t len = size * 8;
+ char *end;
+
+ if (len % 5 > 0)
+ len += 5 - len % 5;
+ len /= 5;
+ str_buf = GNUNET_malloc (len + 1);
+ end = GNUNET_STRINGS_data_to_string (buf, size, str_buf, len);
+ if (NULL == end)
+ {
+ GNUNET_free (str_buf);
+ return NULL;
+ }
+ *end = '\0';
+ return str_buf;
+}
+
+
+/**
+ * Get encoded binary data from a configuration.
+ *
+ * @return GNUNET_OK on success
+ * GNUNET_NO is the value does not exist
+ * GNUNET_SYSERR on encoding error
+ */
+int
+TALER_configuration_get_data (const struct GNUNET_CONFIGURATION_Handle *cfg,
+ const char *section, const char *option,
+ void *buf, size_t buf_size)
+{
+ char *enc;
+ int res;
+ size_t data_size;
+ if (GNUNET_OK != (res = GNUNET_CONFIGURATION_get_value_string (cfg, section, option, &enc)))
+ return res;
+ data_size = (strlen (enc) * 5) / 8;
+ if (data_size != buf_size)
+ {
+ GNUNET_free (enc);
+ return GNUNET_SYSERR;
+ }
+ if (GNUNET_OK != GNUNET_STRINGS_string_to_data (enc, strlen (enc),
+ buf, buf_size))
+ {
+ GNUNET_free (enc);
+ return GNUNET_SYSERR;
+ }
+ return GNUNET_OK;
+}
+
+
+static void
+derive_refresh_key (const struct GNUNET_HashCode *secret,
+ struct GNUNET_CRYPTO_SymmetricInitializationVector *iv,
+ struct GNUNET_CRYPTO_SymmetricSessionKey *skey)
+{
+ static const char ctx_key[] = "taler-key-skey";
+ static const char ctx_iv[] = "taler-key-iv";
+
+ GNUNET_assert (GNUNET_YES ==
+ GNUNET_CRYPTO_kdf (skey, sizeof (struct GNUNET_CRYPTO_SymmetricSessionKey),
+ ctx_key, strlen (ctx_key),
+ secret, sizeof (struct GNUNET_HashCode),
+ NULL, 0));
+ GNUNET_assert (GNUNET_YES ==
+ GNUNET_CRYPTO_kdf (iv, sizeof (struct GNUNET_CRYPTO_SymmetricInitializationVector),
+ ctx_iv, strlen (ctx_iv),
+ secret, sizeof (struct GNUNET_HashCode),
+ NULL, 0));
+}
+
+
+int
+TALER_refresh_decrypt (const void *input, size_t input_size, const struct GNUNET_HashCode *secret, void *result)
+{
+ struct GNUNET_CRYPTO_SymmetricInitializationVector iv;
+ struct GNUNET_CRYPTO_SymmetricSessionKey skey;
+
+ derive_refresh_key (secret, &iv, &skey);
+
+ return GNUNET_CRYPTO_symmetric_decrypt (input, input_size, &skey, &iv, result);
+}
+
+
+int
+TALER_refresh_encrypt (const void *input, size_t input_size, const struct GNUNET_HashCode *secret, void *result)
+{
+ struct GNUNET_CRYPTO_SymmetricInitializationVector iv;
+ struct GNUNET_CRYPTO_SymmetricSessionKey skey;
+
+ derive_refresh_key (secret, &iv, &skey);
+
+ return GNUNET_CRYPTO_symmetric_encrypt (input, input_size, &skey, &iv, result);
+}
+
+
+void
+TALER_hash_context_start (struct TALER_HashContext *hc)
+{
+ GNUNET_assert (0 == gcry_md_open (&hc->hd, GCRY_MD_SHA512, 0));
+}
+
+
+void
+TALER_hash_context_read (struct TALER_HashContext *hc, void *buf, size_t size)
+{
+ gcry_md_write (hc->hd, buf, size);
+}
+
+
+void
+TALER_hash_context_finish (struct TALER_HashContext *hc,
+ struct GNUNET_HashCode *r_hash)
+{
+ void *res = gcry_md_read (hc->hd, 0);
+ GNUNET_assert (NULL != res);
+ if (NULL != r_hash)
+ memcpy (r_hash, res, sizeof (struct GNUNET_HashCode));
+ gcry_md_close (hc->hd);
+}
+
+
+/* end of util.c */
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